Radio loop aerial



Oct. 21, 1930'. J; PROCTQR 1,779,145

RADI 0 L00? AERIAL Filed May -13, 1925 7 Sheets-Sheet l ,BOW JL- Oct. 21, 1930. J. A. PROCTOR 1,779,145

RADIO LOOP AERIAL Filed May 13, 1925 7 Sheets-Sheet 2 INVENTOR Jwm flB rBrocm/ BY G 6 ATTORNEY Oct. 21, 1930. J. A. PROCTOR 1,779,145

RADIO LOOP. AERIAL Filed May 1:5, 1925 I 7 Sheets- Sheet s INVENTOR al a ATTORNEY Jaw/#2551 Pfoarof Oct. 21, 1930. J. A. PROCTOR RADIO LOOP AERIAL Filed May 13, 1925 T Sheets-Sheet 4 R O Y T N E V m V Jmmwiaazzr Rgocrat BY/ 1 ATTORNEY Oct. 21, 1930. J. A. PROCTOR RADIO LOOP AERIAL 7 Sheets-Sheet 5 Filed May 15 1925 NVENTOR Joli/V JLBER 'PQOc rag BY f ATTORNEY Oct. 21, 1930. PRQCTOR 1,779,145

RADIO LOOP AERIAL Filed May 13; 1925 '7 Sheets-Sheet e INVENTOR JOHN/71.85??? i ztocrozt D1 1 t q ATTORNEY Oct. 21, 1930. J. A. PROCTOR 1,779,145

RADIO LOOP AERIAL- Filed May 15, 1925 7 Sheets-Sheet '7 4 Hi INVENTOR JOHN flLBEIET FROG rag ATTORNEY Patented Oct. 21, 1930 UNITED STATES PATENT OFFICE SPECIALTY APPARATUS COMPANY, OF NEW YORK mmo LOOP annmr.

Application filed May 18,

This invention relates to radio loop aerials and radio direction finding, including radio compass structures and methods.

An object of the invention is to increase the accuracy, facility and speed of determination, at a radio receiving station, of the direction therefrom of a distant point at which a radio transmitter is located, which distant point may be out of other than radio communication.

The invention consists of the apparatuses and methods pointed out as to novelty in the appended claims, and described by way of example in the following specification,

in connection with the drawings of which Fig. 1 is a schematic perspective view of my direction finder, including the. compensating apparatus;

Fig. 2 is a diagrammatic View of the elec- 'trical circuits and of various instruments constituting parts of the completely operative direction finder;

Fig. 3 is an enlar ed detail front elevation,

partly in section, 0? the loop-rotating means, the compensator and adjacent parts;

Fig. 4 is a horizontal section on the line 4-4 in Fig. 3, and shows in particular various details of the compensating apparatus;

Fig. 5 is a detail perspective of the ad 39 justable band, roller and roller arm of the compensating apparatus;

Fig. 6 is a horizontal section on the line 6-6 in Fig. 3, and shows certain details of the loop-rotating and locking mechanism; also means by which the position ofthe loop is made known visually to the operator;

Figs. 7 and 8 are detail vertical sections on the lines 77 and 8--8 respectively in Fig; 4, and show details of the collector rings for the'electrical circuits;

Fig. 9 is an enlarged detail elevation partly in section, of the loo showing the mechanical construction 0 the loop housing bearing and supporting flange;'and,

Fig. 10 is an elevation, partly in section, of the tripod device by which the loop can be elevated above the roof-ofthe radio-operators cabin.

Heretofore radio direction findin in practice has involved the employment 0 a rotata- 1925. Serial N0. 29,919.

ble closed-circuit, condenser-tuned aerial, (Pickard Patent 876,996), the closed-circuit aerial or loop being rotatedas a bi-lateral functioning loop to obtain the line-bearing, and then mechanically rotated as a unilateral loop to obtain the sense-bearing. The apparatus has been such as toresult in such serious errors as to the line-bearing as not only to result in an inaccurate line bearing, but in some cases to cause the sense-bearing based thereon to be of little or no value. The reason why the bearings obtained by prior apparatus and methods were not the true bearings is that the operation of the receiving loop is aifected by electrical conductors in the vicinity of the radio receiving station, which cause distortion of the wavefront approaching the loop; such distortioncausing conductorsbeing especially vertical conductors, such as shrouds, stays and funnels;of a steamship, but also other conductors, even underground pipes in the vicinity of land radio stations.

It is important that the direction-determination be not only accurate but speedy, as in cases of location of a ship at sea in storm, and it is desirable that the determination be made with the minimum of movement of the heavy slow-moving loop structure itself. Heretofore it has been the practice not only to rotate the loop in the process of determm- OF BOSTON, MASSACHUSETTS, CORPORATION p ing the sense-bearing, as well as in the process of determining the line-bearing, but it has been the practice for the operator after the determination of the line-bearing to correct the same for distortion errors, such'correction having beenmade with the assistance of a curve sheet, chart or table previously prepared for the particular direction finding apparatus in the conditions of its installation environment. This correction, however,

made by the radio receiving operator, not

only consumed considerable time, frequent- 1y vitally important, but permitted errors of personal observation involved in the making of the corrections themselves.

, In accordance with the present invention, the distortion-errors are corrected by the operation of the apparatus itself .in deter-' mining the line-bearing prior to the determination of'the sense-bearing; and the sense bearing is determined thereafter on the basis of a true line-bearing, not requiring correction by the operator, and by a method which makes unnecessary the mechanical rtation of the loop for the determination of the sense-bearing, such new method being extremely effective, in connection with the 4 automatic error-correction, in increasing the accuracy of determination of the sense-bearmg.

In Fig. 1 is shown somewhat diagrammatically for clearness the assembled selfcompensating radio compass or direction finder; and Fig. 2 is a diagram showing the electrical apparatus and connections employed with the direction finder of- Fig. 1 in connection with the novel method for the accurate determination of the sense-bearing without mechanical rotation of the loop.

In Fig. 1, the loop L is fixed mechanically on the upper end of a rotatable vertical hollow metal (as brass) shaft'H down thru which the insulated loop-leads extend (Fig. 9) and from the lower end of which said leads exit (Figs. 3, 7 and 8) to the electrical apparatus of the diagram of Fig. 2.

A second vertical rotatable hollow shaft H (Figs. 1, 3 and 9) is located below and in hne with upper shaft H. To a lower portion of shaft H is keyed (Fig. 1), to rotate therewith, an operators indicator OP (Figs. 1 and 2), which revolves over the manually rotatable compass card OS and scale IS. Said card and scale may be illuminated from below to facilitate accurate observation, because this indicating means provides direct accurate readings for the' line-bearing and sense-bearing respectively.

Operators indicator-4.0]? has not only the long pointer L usually employed in determg the line-baring, but also a short pointer S, S used thereafter in determining the sense-bearing. Indicator OP preferably, as shown, is fixed to lower shaft H so that its line-pointer L is more or less at right angles to loop L,.depending on the actions of the compensating mechanism now to be described.

A flexible metal band B (Fig. 1) is fixed in a horizontal plane between the adjacent ends of thetwo shafts H and H Shafts H and H are connected together to permit joint rotation, but at dissimilar rates, by mechanism which includes (Figs. 1, 3, 4 and 5) a roller R acting on the inside I of band or curve B, the roller being pressed a ainst the band B by a suitable spring D igs. 1, 3 and 1). This is an improved embodiment of the inventions in my application for patent Serial No. 408,291, filed September 4, 1920;

The shape ofband B and the operation of roller R on the.side thereof control the angu-' lar movement of shaft H for a given angular movement of loop L and shaft H Shaft H is the one which usually is rotated by the operator as by hand-wheel HW (Figs. 3 and.

6) in the determination of the line-bearing. Band B may be substantially circular when the entire apparatus is first installed in its place of use, as on a steamship. As part of thefinal process of installation, band B, in

preparations for future operations, is given rors. .The observing radio operator, to determine the line-bearing, simply rotates loop L mechanically and reads the true line-bearing by the position of operators pointer L on the scale 1S Pointer L fixed to shaft H (and more or less at right angles to loop L of shaft H then will indicate the true line-bearing notwithstanding that the position of loop L itself does not indicate the true line-bearing.

The mechanism'connecting shafts H and H and including roller R is important and is as follows (Figs. 1, 3 and 4) An arm A fixed at its inner end to loop-shaft H to be revolved thereby has its outer end pivotally connected to one end of a link K, the, other end of which'is pivotally connected to a second arm A at a point intermediate the ends of the latter. Cne end of second arm A is pivotally connected with the outer end of a third arm A. The inner end of third arni A is fixed to lower or pointer-shaft H at the'upper end thereof to rotate said shaft H when, as preferred, the rotation of the Thereafter, flexible band.-

carries roller R, and spring D forces roller R yieldingly against band B.- t

The general operation of this compensating apparatus connecting shafts H and H is-as follows, it being assumed that curveband B has been set by the installer (see later for description the'reofiiin accord with distortion errors due to the, environment of aparticular loop L and/or itscircuits of Fig. 2. The operator or observer (band B prevlously having been set by the installer) mechanically rotates loop L to determine the line-bearing of the location of the distant radio transmitter (pointer L on scale IS). Shaft H via the compensating mechanism above described, rot-ates shaft H at rates which slightly differ from its own. rates, depending upon .the departures of parts of curve-band B from a perfect circle centering ly in line with the loop, or at more or less departures from line, depending on said errors and the corresponding departures of parts of curve B from the periphery of a perfect circle. WVhen, as preferred, pointer L initially is fixed to shaft H at right angles to loop L, the line-bearing of the distant transmitter is determined by aural observation of minimum or null telephone response, when loop Lis at right angles to the line-bearing; and the position of pointer L will be substantially in exact line with the distant radio transmitter, and therefore, will indicate on the scale of degrees of a circle (OS) and'at null loop response, the true line-bearing of said transmitter, and what is of importance, the line-bearing of the ship or the shore station on or :at which said transmitter is lo-' cated.

In effect, therefore, there is incorporated within the loop-apparatus itself the curve of distortion errors which heretofore has been in the form of an independent diagram or chart but which curve now is made a functioning part of the loop-apparatus itself. 0

There are two customary methods of taking a line-bearing. One is by reading the compass card OS and scale IS in degrees ofl' the keep or ships head, and the other is reading from the ships course at that instant. Either method may be used with the apparatus hereof. In both methods (referring to Fig. 1), the operators scale IS is fixed in position so that the pointers therein (arrowheads, Fig. 1) are in line with the keel of the ship (keel-line LL, Fig. 1). Compass card OS is manually rotatable.

In case it is desired to employ the first method, i. e., to take a reading direct from the ships head (i.' e. from keel-line LL),

then compass card OSis used in a position where its zero and 360 degree marks lieon keel line LL. The position of operators pointer-L then-will indicate the line-bearing of the distant radio transmitter, in degrees from keel-line LL.

In case it is'desired,to employ the second method, i. e., to obtain a line bearing figured in degrees from the ships course at any instant, then compass card OS is rotated by the operator to a point which coincides with the course in degrees from the ships head as given by the navigator to the radio operator at that instant.

The compass card OS shown as forming part of the operators indicator in Fig- 1,

ordinarily is supplied with the direction finder hereof; but it may be replaced by a magnetic compass suspended below operators pointer L in a similar manner; or a gyroscopic repeatermay be employed in like manner. With either of these instruments, line-bearings indicated by the'positionof operators pointer L will be direct with respect to the ships course and will coincide with the master navigatingcompass.

The circuit diagram (Fig. 2) shows the coordination with the mechanicalapparatus of Fig. 1, of the electrical circuits of the loop L and its associated radio apparatus. The lower shaft'H shown in Fig. 1, is omitted from Fig. 2 for clearness.

The general method of operation and the I novel method for determination of the sensebearing now will be described in connection particularly with the diagram of Fig. 2, it being first assumed as follows. Short operators pointers S, S (Figs. 1 and 2) are indicators of the sense-bearing; long operators pointer L? permanently at right angles to S, S being, as stated, an indicator of the line-bearing. Either S or S is pointed ninety degrees off from the distant trans.- mitter when pointer L is in line-bearing position.

Before the determination of the sensebearing, but after the line-bearing has been determined by the reading indicated by pointer L at minimum or no loop response, the rotatable loop system is turned ninety degrees so that the sense pointers S S point to the same readings of operators scale IS as those which have just been indicated bypointer L This, of course, can be done with perfect accuracy.

In this operation loop L will be rotated mechanically from its broadside front to the distant transmitter, so that its plane will be brought in line with the distant transmitter, more or less, depending upon the dis- .tortion errors. Up to this time loop L has been acting as a bilateral loop,'the switch S of Fig. 2 having been pointed at the point marked Line, i. e., in a position where the switch established pure or bilateral loopconditions, for the purpose of determining the line-bearing; the loop as a bilateral loop thus having two points; of maximum response (either end) and two points of minimum response (either side); altho the critical obtransmitter. Now, sense pointers S, S? are provided for the purpose of cooperating with the electrical switching means of Fig. '2 for the purpose of determining the sense-bearing, i. e., determiningwhether S or S is pointing at the distant transmitter, by observation and comparison of the loudest signals. with the weakest or minimum, the loop acting uniservation-of line-bearing at null response was in the loop position broadside on the distant laterally, i. e., with a blind spot at one end.

-At this time, when the, sense-bearing is about to be determined, the operator moves switch S to one or the other of the two sense positions, i. e., either red or white, as shown, Fig. 2. At either red or white position, the loop L is changed (sce later for how) from a bilateral to a unilateral loop for the purpose of causing it to have only one point of maximum (only one end) and only one point of minimum (the other end) response. The operators sense pointers, S, S of Fig. 1 are colored red'and white, respectively, to correspond with the red and white sense positions of switch S of Fig. 2. That is, they are adapted (pursuant to a manufacturers test to be described) to indicate correspondence to a sense (as vision) of the observer.

.At this moment pointers S S are more or less in line with loop L, their departures from line depending on automatic correction of distortion error by the compensator; w The loop L itself has one of its ends pointing more or less toward the distant radio transmitter, the departures, from exact pointing thereat depending on the distortion errors.' The question now is which end of the loop, i. e.,

"which of the two sense pointers S S is pointing at the distant radio transmitter, the red pointer S or the whitepointer S This is determined by the aural sense of the observer via phones P in the diagram of Fig. 2, while switch S is moved by him successively to the red or white (S or S positions; and this without any mechanical rotation of loop L to change the physical relation of its'parts to the distant transmitter;

lhe result of the operation of switch S is, so to speak, an electrical rotation of loop L. The advantage of this electrical rotation is twofold,'- for it not only obviates the need of actual and slow movement of a comparatively heavy loop structure by the operator wvhile he is making visual or aural observations, but,

.- what is of greater importance, it obviates the I t me lag between different loop positions and corresponding presentation of diflerent sound intensities to the operators ears for his udgment as to difi'erences' in intensity.

That is, the operator can move switch S from' red towhite positions very rapidly indeed, as compared with mechanical rotation of the loop structure, and such rapid operation of the st tch permits the two sounds' of'difl'erent intensities to be compared or contrasted by him with minimum time interval,

thereby permitting very greatly increased accuracy of aural observaton. v

The above electrical rotation of loop L results from the following conditions. In either the red or white (sense) positions of switch S, its blade 1 connects re- I sistance R in the grounded open antenna circuit between ground G and a mid-point X of loop L, This results in producing the corsaid antenna-currents.v Thus, the maximum and minimum'points of the uni-lateral loop are shifted through 180; in other words, loop L is turned electrically end for end.

Now, assume switch S to be in the white sense position, as shown in the diagram of Fig. 2, and that in fact the distant transmitter is at the left end of loop L marked red'in Fig. 2, the direction of waves from the distant transmitter being indicated by the arrow. Assume, also, that the maximum'of the uni-lateral characteristic of the loop (switch S being, as stated, in the white position)=is in "line with. the loop and at its right or end marked white, due to the direction of winding of the loop and thepoling of the various circuits connected to theloop and its amplitying apparatus U. Then the minimum of uni-lateral characteristic will come in line with the loop and at the left or loop-end marked red. phone-s PH with switch S in white sense position, will hear nothing or a faint signal; but when he moves switch S overto the red position, he .will hear a strong or much stronger signal, because in that position of the switch the loop circuits are such as to give a maximum response to signals coming toward the red end of the loop. The receipt of maximum signals at the red po 'sition of the switch (Fig. 2) and the senseto-operator correspondence of the red switch position with the red sense 'pomter S (Fig. 1) v and the automatic error-d1scounting oi the apparatus, will indicate to the operator the fact that the distant transmitter is exactly in the direction toward which red pointer S of Fig. 1 is pointing.- Thus, the

solute accuracy based upon the accurate predetermination of the line-bearing.

tors sense pointers S, S of Fig-.1 are oppositely colored in correspondence with the oposite coloring of the positions of switch S,

sense-bearing. is determined without me-. chanical rotation of the loop, and with ab- The observer, listening at In the process of manufacture, the operais in the white sense-position, and at minimum or zero response of phones PH. If white pointer S is not-so pointing, then the terminals of loop L are reversed, (as a step of manufacturing or installing) either at the receiving apparatus or at the collector rings shown in Fig. 3 such reversal resulting in coordinating the operators sense-indicators S S of Fig. 1 with the switch positions of Fig. 2.

The mechanical apparatus and the loop aerial of Fig. 1 may be employed with electri-- m1nimum or zero when the pointer which is to be used to indicate the sense-bearing (as either S or S reaches the position in which it points at the known distant transmitter. If the minimum or zero response does'not occur in such position of such pointer, the installer will reverse the terminals of loop L, as above described, and that will result in fixmg conditions so that such pointer thereafter will act as the sense pointer.

The sense pointers S, S of Fig. 1 are useful during periods of occurrence of what is lmown as night effects, when it is not practicable to dlstmguish nul loop points in bilateral workmg on account of the fact that re- 7 sponses of more or less equal intensity result from allangular positions of the loop. Under such cond tions, however, there is good loop-working under uni-lateral arrangement.

In such cases, therefore, pointers S S fixed more or less in the plane of the loop L, (the loop being more or less in line with the distant transmitter), may be used not only for determmation of sense-bearing,

but also initially for determination of line-bearing, by the operators pbservation of the signal minimum or nul loopresponse. Hence, the sense-bearing may be determined, as above described, but without the preliminary 90 mechanical rotat on of loop L. In fact, this operation can be eifected not merely at times of night effect, but at any time, including times of heavy static. Usually, however, in the day time it is preferable, for determination of line-bearing, to use pointer L in connection with bilateral loop-working (with switch S of Fig; 2 in line position) and observation of mini- .mum or nul response of loop at right angles to the distant transmitter. This preference 1s due to the far greater accuracy of .bi-lateral working in direction finding, due to the fact thatthe 111115 or are far sharper m bi-lateral working than in uni-lateral work ing, save under the night or static conditions above referred to.

The following are the important details of the apparatus of the diagram of Fig. 2. TC is the loop tuning condenser, used for all positions of switch S. Resistance R is in circuit with loop L only when the latter is in condition for uni-lateral reception (switch S at positions sense red or sense white). The function of resistance R- is to add an openantenna component to the true loop-current. O0 is a condenser of small capacity, which transmits the open-antenna current (with R in circuit) to amplifier U. lCondenser OC always is in circuit; but when switch S is in position marked Line (for bi-lateral loopworking) there is no open-antenna E. M. F. across condenser OC as there is when switch S is in a sense position, The values of resistance R and of condenser 0C are determined by test for each designed embodiment of. the invention. Initially, during manufacture, these values are varied until with signals from a known distant transmitter and with switch S in positions S S respectively there is maximum different intensity of sound in phones PH in said two switch positions. The value of resistance R is of the general order of 1,000 ohms, say from 500 to 1,500 ohms, more or less. The value of condenser 00 is of the general order of .0001 microfarad, more or less.

' The apparatus can be used for ordina recepti on wh en switch S is in either of the t ree positions of Fig. 2. g a.

After sense-bearing as well as line-bearing of a given distant transmitter has been determined and reported to an inquirer, and when the line-bearing of another distant radio. transmitter is to be determined, then switch S is moved to its position marked Line (Fig. 2). This results in short-circuiting resistance R from the circuit.X--G, leaving that good grounding circuit from mid-point X of loop L for the purpose of eliminating all open-antenna action, and leaving the possibility of only true loop currents for bi-lateral loop-working, preferably with minimum or nul loop response, this being the optimum condition for determination of line-bearing.

Summin u the action of switch S is as follows. la e 1 outs resistance R out of circuit or shorts it, when switch is moved to line position from either red or white position. Each of blades 2 and 3, when moved either from red to white or white to red, reverse the terminals of loo L with respect to variable loop-tuning con user TC, amplifier U, and the ground- ]agh" X-G through small fixed condenser The operations in installing the apparatus with articular reference to the setting of band of the compensating apparatus, are as follows. It is to be assumed that the installation is complete save for such band adjustment, and that flexible metal band B is substantially circular. Fig. 5 shows the preferred duplex construction of the band, which comprises two bands B and B arranged edgewise one above the other, and each with disconnected ends (i. e., each band is split), the two disconnected ends being located at different portions of the circle, thereby permitting the radial deformation of band B as a whole, without completely interrupting the continuity of the inner band sur ace over which roller R operates. Each band is about 3 /8th of an inch wide, so that the two provide a total vertical width of about 3/4ths of an inch for roller R of more or less correspond- "ing width, so that the roller R travels over both bands. Each band B, B of band B is of thin phosphor-bronze about 3/64th inch thick, so that band B is flexible. The object of this part of the installation is to deform band B in accord with previously observed distortion errors, thereby causing band B itself to be in effect an error-chart or diagram embodied as a functioning part of the apparatus. With thislconstruction and otherwise complete installation, the final installation operations are as follows. (1) The installer selects a known radio transmitting station, as one in sight. (2) He arranges for it to transmit test signals for a sufficiently long time. (3) If the installation is being made on a ship, the shipv is then swung slowly around thru a circle of short radius. (4) At freuent intervals during such movement of the 's ip (a) the installer observes the apparent bearings of the known distant transmitter by the aid of loop L, and',(b) simultaneously the shi s navigator makes pelorus observations 0 the bearing of the transmitter, and, (a) they either transmit their observations to one another at the time, or (d) record them for subsequent comparison. (5) Forecouracy, these observations of theinstaller and navigator are repeated several times to; check errors. If the direction finding apparatus is being installed on land, then the land operator arranges for the distant radio transmitter, say on a ship, to sail a course covering all desired angles with respect to the land di-J- rection finder; then the land installer makes simultaneous observations, by pelorus and radio direction finder. Then the errors are observed and recorded as by tabulation or by correction curves, and finally embodied in corresponding distortion of band B, as de: scribed later.

In making the above observations by radio compass, the installer does the following. (1) Rotates loop L until he hears minimum or no response in phones PH. (2) Reads the position of installers pointer IP on installers scale IS. The zero of scale IS is in line with the ships keel or lubber line The installer, now equipped with the data of observation, proceeds as follows." He sets his pointer I]? at zero or other point of scale IS. As yet, while band B is substantially circular, the lower or operators pointer OP (as L thereof) points to the same number of degrees on the lower or operators scale IS as does upper installers ointer IP on the upper installers scale I ,the two scales being fixed alike as to the ships lubber line LL. With the two pointers IP (above) and L (below) at say zero degrees on their respective scales, the installerlooks at his record of distortion errors of this apparatus for zero degrees reading and finds, for example, that the true bearing of the known distant transmitter at zero degrees setting of the loop L-was actually 5. The installer then observes the position of roller R, which may be at any angular position against roller band B. He then (Figs. 1, 3 and 4) turns screw- E on one of the adjusting devices F which is located in the vicinity of roller R, thereby bending band B inwardly or outwardly until;

the resulting movement of spring-pressed roller R moves lower shaft I-I so that operators pointer L moves from 'zero degrees toward and to 5 on operators scale 13 When this position is attained, the adjusting screw E is fixed for permanent installation for this particular part of band B. If roller R happens to lie between two adjusting screws, the installer adjusts both screws. It is preferable to provide about 2 f adjusting devices with their adjusting screws around the circle of band B of about ten inches g 4). The above adjusting of band B is repeated thruout its circumference and in ac- ,cordance with the table of errors prepared as the result of the above observations of the installer and the navigator.

The change in amount of error, in traversing the entire scale, is gradual, i. e., there is usually no large change of error for a small change in degree of arc. The flexible metal band B and its adjusting devices are of such rohstituency as to give only smooth and gradconforming to the above fact as to the errors. Thus, consequently, .while there may beseveral bulges in theresulting adjusted band, B, the resultiisr'more likely to be 'what might be termed a smoothlybumpy circle. That is,

"ual departures froma circular are, thereby f the adjusting movement 'of one screw is not very greatly different from that of the screws adjacent to it, even-where the error changes sign, i. e., where tHF-band is bent inwardly and outwardly reszectively. In adjusting around the circle, the successive adjustments may be made at no more frequent intervals than 10 apart, although the adjusting decabin for the determination of the side the upper part of flange T (a lower ballvices and adjustments may be made closer, provided to permit installation of standard f deslred. The result is an installation which apparatus in cabins or pilot houses of varying is permanent so long as there is no substanheight, permitting the location of the comtial change in the matter of electrical conducpensating apparatus and indicating scales tors in the vicinity of,the direction finder. of Fig. 1 (carried with shaft H by any suit- In case of any such change, it is desirable to able supports bolted to the floor) at substanrcpeat the above portion of the installation tially the same distance above the floor in including the observation of errors and the every instance. In manufacturing, the holresctting of band B. low shaft H (Fig. 9) is made of maximum The mechanical operation of the compenlength and is formed with a vertical series sator including bandBis as follows. Motion of horizontal rows of jig-located holes 1. of the main operating shaft H (Figs. 1 and In installation the top of this shaft H is cut 3) is transmitted to indicator shaft H by oil (if the head room is less than maximum) means of the link motion. Torsion spring D so that lower holes 1 of the vertical series of keeps roller R always in close contact with holes may receive screws 2 securing shaft the inner surface of band B. In order that H to the rotatable hollow loop structure.

a given bulge of band B inwardly or out- Similarly fixed metal tubeQ, (Fig.9) in manwardly from its original circular configuraufacture is made of maximum .len th and is tion willregister equal degrees and correction formed with jig-located holes 3 in orizontal from the pointer (L attached to shaft rowsand in similar vertical series of rows, (H the center of roller R is .designed to so that in installation the top of this tube Q. move in and 'out on a radius passing thru the may be cut off, and yet bring one horizontal center of shafts H and H It is also desirset of holes 3 in position to receive screws 4 able to have the included angle, formed by which re tube Q to fixed'supporting tube A and K, equal to 90 degrees when the band P dependingfrom flange-member T. Thus V B is a perfect circle of mean diameter. It is the rotatable and fixedparts between the floor likewise desirable to have the included angle n the compensating ap aratus and scale=inbetween the. links (A and A") 90 degrees dicators may be made su stantially the same, under similar conditions. By maintaining irrespective of the height of the cabin, and the angles given, the most v riable mechaninotwithstanding the fixing of a part of the cal leverage systems are possible, that is, the structure of the roof of the cabin, and therelinks are always asfar as possible fromtheir by bringing the apparatus and indicators at dead center position. substantially the same height in call cases The various more or less important further *relative to the operator. features of actual embodiment of the in- In Figs. 3, 4 and 6 are shown the details of ventions hereof are shown in Figs. 3 10, ac- .the mechanism for rotating the loop structure cording to the general descriptions of such and for. locking it against wind-pressure.

figures first above stated. Gear teeth are located 'on'the loop-rotating In order to place the apparatus in its deshaft and a worm gear 5 is lreyed on h0r1- slred place of operation'(as wifihthejs ructure zontal shaft 6 to engage said teeth, hand of loop L above the cabin roof an'diwiththe 'whel HW lying inside the cabin on the end rest of the structure in doors), it is onl of shaft 6 so as to be arrangedvertiqally for necessary to provide an openin iii the roof the greatest convenience of the operator read- JdFigs. 9-10) to permit passage of -the' 'lon\- ing the indicatin scales. (If desired; handitudinal portion of the roof-casting PzaiThe wheel HW may be mounted horizontally d1- orizontalflange portion T of such roofg'c'astrectly on shaft H but the above gear reducing then is bolted to roof J ,a rubber or other tion is preferred.) The reduction gear ng 1s g sket V (F' 9) being interposed betw enclosed in a casing '7. Between casmg 7 roof J and ange T. Thus vertical hailsand hand wheel HW is located a friction lock wheel HW Fig. 3) inside the cabinor, house can be operated to rotate the 00p jsl l i structure enclosing lgop'wires L, outside the yjwind 01' otherwiseilot which clamps the latter in any desired pothereby fixing the loop from rotation On wheel HW and ing; yet the apparatus inside the cabin is to thopera or inside the cabinagiven desire protected from the weather. In Fig. 9 are n rm l d shown the practical features'of the top ballthe roof, such osition be ng that for example bearing for the rotatable loop structure inof minimum-'- 1nd resistance such as a fore and aft position one. steamship. bearing is shown at 11, Fig. 3') In Fig. 9 also The compensating apparatus is enclosed m are shown the loop leads Z (Fi 4) from a casing 10 as shownj n detail in Fig. 3. loop L extending down thru hilow shaft In Fig. 10 is shownalateral supporting H to the collector rings. of Figs. 7-8. Also means for the loop structure above the cabin in Fig. 9 is shown the hollow metal loop roof J in a case where it is desired to have structure enclosing loop wires L., the loop structure more elevated above the The following adjustment construction is oof th i Fi 9, Thi means comprises position of the loop outside on liiie-bearlocks-are marked arrows 9 (Fig. 3 indicating legs or links 18 pivoted at their upper ends to a stationary head or support 12 supported by them and in turn supporting top bearing for the rotatable structure. Legs 18 are pivoted at their lower ends to feet 13 bolted thru roof J. In this case the loop is centrally supported by a metal tube 14, which is rotatable by being secured at its top, as shown, to the bottom of the hollow loop structure L (rotating on top bearing 15) and secured at its bottom as shown to a structure rotating on lower bearing 16; shaft H being secured to the hollowloop structure L to rotate therewith. Tube 14, therefore, constitutes an upward extension of loop-rotating shaft H Legs 18 preferably, as shown, have a turnbuckle construction 17 (Fig. 10), so that, in combination with their pivots, the loop may be very securely positioned at a substantial distance above cabin roof J. All this construction is optionally additional to that in volving roof-flange T above described.

As to'the compensator and band B, while the latter is shown stationary, the part rotated by the operator being shaft H yet it is to be understood that various other arrangements are within the scope of the invention. That shown, however, is preferred on account of varlous practical considerations. With this construction, for example, it is the heav- 1er part of the structure (the loop structure whlch also frequently is subject to wind-pressure) which is rotated and it in turn rotates the lower shaft H via the compensator, the parts of which, therefore, may be of lighter construction than in the case where the operator rotated the lower shaft H in the first instance. Also as contrasted with a modificat1on wherein a rotation of band B (against a roller fixed relative to loop L, band B and the indicating scales), the band B here may be much lighter in construction and, therefore, more readily adjustable by the installer to distortion errors.

The loop structure as to general dimenslons is standard, being a coil about 4 feet square and having a suitable number of spaced turns, or otherwise, all as well known.

While this invention is embodied in the preferred form, which comprises a single rotatable loop-coil, yet the various features may be employed with various other forms of radio loops, including the form comprising a plurality of fixed loops and a rotatable search-coil; in such a case, the compensating apparatus hereof being combined with such rotatable search-coil.

All the uses of the invention are included within the scope of the claim, as for example its use for ordinary reception, including reduction of interference (by radio transmitters orstatic), due to the directional and/or unilateral properties of the loop; and vanous other features for any desired purpose may be combined with the disclosures hereof.

.I claim:

In radio loop aerial apparatus, the combination with a rotatable loop and a shafting rotating therewith, of a second shaft and an indicating device for the second shaft;

and compensating mechanism connecting the 7 band.

7 JOHN ALBERT PROCTOR. 

